Drafting frames of the aforedescribed type are intended to draw out and increase the fineness of the sliver prior to feeding the same to the spindles of a roving frame and, where the drafting frame is of the type described for example in German patent document 43 23 472 C2, the drafting frame may have at the output side for each strand, a sliver-compaction unit which generates a lateral compaction of the sliver before it is supplied to the ring or traveler or spindle unit for spinning. The result is a so-called compaction spinning of the textile strand.
For such compaction spinning, a variety of devices have been proposed. For example, the compaction unit may operate pneumatically, i.e. with a compaction belt associated with the upper and/or lower array of rollers or belts and which is formed with an row of holes extending in the direction of travel of the textile strand, i.e. the sliver, and communicating with a chamber to which suction is applied. A belt of the type can be provided in conjunction with a roller as the final compaction stage of the drafting path or in combination with another similar belt.
Whichever approach is used, the row of holes should be provided at least in the belt associated with an upper roller.
Under certain circumstances, it is desirable to dispense with the compaction function of the drafting frame. This cannot be done simply by cutting off the suction to the compaction unit at the output end of the path of the sliver through the drafting frame because the mere presence of the compaction unit contributes to a compaction in the final stage of drafting. It has been found to be problematical to simply replace the compaction unit by a simple roller because in that case, there is insufficient guidance of the sliver and experience has shown that the quality of the thread or yarn which is produced is detrimentally affected.